The invention relates generally to medicine, or more particularly to methods of non-invasive investigations of living organisms, and more specifically, for diagnostics of pathological changes in tissues of human and animal organisms.
A number of methods of medical diagnostics, which employs transillumination of organs and tissues by radiation, are known. One of the most widely used is X-ray diagnostics (see Physics of image visualization in medicine. C. Webb, ed., vol. 2, p. 382, Moscow, Mir, 1991 (Translated from English)) but this method is not safe for a patient and the serving personnel, since sources of ionizing radiation are used during the corresponding procedure.
The above mentioned disadvantage is not applicable to ultrasound diagnostics (see U.S. Pat. No. 4,434,799 cl. A 61 B 10/00, NKI 128 660, 1984) which is a non-invasive method, practically harmless both to patients and personnel. It permits revealing sufficiently small pathological growths (about 3 mm diameter) (see The comparison of the sensitivity of ultrasound echo and shadow methods for determination of calcification of breast tissues/ Proc. Conf. Ultrasound Biology & Medicine--Ubiomed. YI, Warsawjablonna, Sep. 19-23, 1983, pp. 41-49). However, this method is sensitive only to the acoustic "contrast" of pathological tissue, which is often insufficient to identify the type of the pathology.
Good possibilities for identifying the type of the pathological tissues may be possible by optical spectroscopy. The method closest to the present is a spectral method of optical diagnostics of internal organs, based on transillumination of the investigated organ by radiation of the near infrared (NIR), 0.6-1.5 um wavelength range and recording of the intensity of the transmitted illumination at several wavelengths. The presence of a "shadow" or a change in the photodetector output signal serves as a criterion of the pathology. This method may be considered similar to the present method and equipment.
This method, has however, considerable disadvantages over the present invention: strong scattering of optical radiation in tissues, provoked by their micro-inhomogeneity, does not permit revealing a pathology growth in the investigated organ depth, if the growth size is much less than the distance separating it from the organ front and bottom surfaces.
The known apparatus for the realization of the transillumination method (see U.S. Pat. No. 4,807,637, cl. A 61 B 6/08, NKI 128-664, 1989) contains an NIR-radiation source with an optical system and a photodetecting device, coupled to a recorder. The investigated organ, a mammary gland, for example, is placed between two transparent plates, compressing the organ and shaping it into a plane-parallel, trapezoid or other forms. The means of moving the "NIR-radiation source--photodetecting device" pair over the organ surface are also available. The main disadvantage of this apparatus is its low sensitivity in revealing the pathology at an early stage due to the above mentioned strong scattering of NIR-radiation by biological tissues.
The task of the invention is elimination of the above mentioned disadvantages of the prototype, i.e. to achieve increasing in the spatial resolution under the conditions of a strong optical NIR-radiation scattering by the investigated tissues.